5.5 Antibodies Flashcards
What is an antibody ?
~ proteins with a specific 3D tertiary structure which is complementary to a specific antigen, synthesised from B cells.
What is the structure of an antibody ?
~ Antibodies are Y-shaped molecule made up of 4 polypeptide chains - one pair is made up of short chains called the LIGHT CHAINS. the second pair is made up of long chains called HEAVY CHAINS.
~ The antibodies have a CONSTANT REGION which is the same on every cell ( used to bind to receptors on cells such as B cells and phagocytes)
~ VARIABLE REGION- has a unique structure so it is different on every antibody molecule ( used for antigens to bind to)
~ HINGE REGIONS- allows the branches to move away from each other so the antibody is more flexible and can bind to multiple antigens.
~strong disulphide bridges are present holding the structure together
How do antibodies cause destruction of the antigen?
~ they act as markers by attaching to pathogens and then stimulating phagocytes to engulf the pathogens which are attached to the antibody
~ AGGLUTINATION~ Antibodies can bind to multiple antigens due to the double binding sites and therefore clump the pathogens into one big group, making it easier for phagocytes to locate them
What is a monoclonal antibody ?
~ monoclonal antibody are antibodies produced from a single group of genetically identical B cells, which are all identical in structure
How are monoclonal antibodies used medically ?
~ they can be used to target specific cells/substances e.g. cancer cells
~monoclonal antibodies are produced that are specific to the antigens on cancer cells
~these antibodies are given to the patient and attach themselves to the cancer cell receptors
~ once they attach themselves they block the chemical signals that stimulate their uncontrolled growth
Advantages of direct monoclonal antibodies therapy
~ not toxic
~ highly specific
~ fewer side effects
How are monoclonal antibodies used in pregnancy tests?
~ when a women is pregnant her placenta produces the hormone hCG, which is present in the urine
~on pregnancy test monoclonal antibodies are present and are linked to coloured particles
~if hCG is present in the urine it binds to the antibodies forming a antigen-antibody complex
~ the urine moves up the stick carrying the coloured particles with it
~the test strip contain immobilised antibodies to hCG
~ if there is hCG present the test strip turns blue due to the immobilised antibodies binding to the hCG
What are the ethical issues of the use of monoclonal antibodies?
~ production of antibodies involves the use of mice, some people may think harming/ using animals in this way is unethical
~side effects - no full knowledge of the risks
~issues about conduct trails
How are monoclonal antibodies produced?
~a mouse is exposed to the non self material (pathogen) which an antibody is required.
~the B cells in the mouse produce a mixture of antibodies which are then extracted from the spleen of the mouse
~these B cells are mixed with cells that divide readily outside the body (cancer cells) in order for the b cells to divide
~detergent is added to the mixture to break down the cell surface membrane of both cell types so they can fuse together. The fused cells are called hybridoma cells
~the hybridoma cells are separated under a microscope and each cell is cultured to form a clone, each clone is then tested to see whether it is producing the required antibodies
~the clones which produce the required antibody are grown on a large scale and extracted from the growth medium.
~ monoclonal antibodies are produced
^^~ as these cells come from mice they have to be modified for human use to make them like human cells( humanisation)
Why are monoclonal antibodies useful in medicine?
Only bind to specific target molecules / antigens because…
- Antibodies have a specific tertiary structure (binding site / variable region) that’s
complementary to a specific antigen which can bind/fit to the antibody
